Adhesion to lithium disilicate glass-ceramics after aging: Resin viscosity and ceramic surface treatment effects.

OBJECTIVE: To evaluate the influence of intaglio ceramic surface treatments, resin cement viscosities, and storage regimens on the microshear bond strength of lithium disilicate ceramic. In addition, to investigate the dynamic viscosity of the resin-based luting agents. MATERIALS AND METHODS: Ceramic slices were randomly allocated into eight groups (n = 19) considering three factors: ceramic surface treatment (hydrofluoric acid followed by silane, HF; or self-etching ceramic primer, E&P), resin cement viscosity (high, HIGH; or low, LOW) and storage regimen (baseline or aging). Surface treatments were performed, resin cement cylinders were built and microshear bond strength tests (µSBS, wire-loop method, speed: 1.0 mm/min) were run according to the storage factor. Failure mode, topographic and dynamic viscosity (37 °C; shear rate of 1.0-100 s-1) of resin cement components (base, high and low catalyst) were also performed. RESULTS: Resin cement viscosity and the association among ceramic surface treatment, resin cement viscosity, and storage regimen were statistically significant factors (p < 0.05). Worse behavior was identified for the E&P_HIGH group compared to the E&P_LOW and HF_LOW in the baseline condition. After aging, the HF_HIGH group (16.78 MPa) presented the worst result among the aged groups (21.44-25.25 MPa). Most of the failures were adhesive. Surface micrographs revealed a distinct pattern after etching, more aggressive by HF and milder by E&P. High viscosity catalyst is 5.3 and 8.5-fold more viscous than the base and low viscosity catalyst, respectively (high > base > low). CONCLUSION: Differences in filler content can impact the resin viscosity of the material (more fillers increase the viscosity), which in turn can influence the bond strength of a lithium disilicate ceramic, depending on the surface treatment and storage regimen.

Design and Characterization of Maltoheptaose-b-Polystyrene Nanoparticles, as a Potential New Nanocarrier for Oral Delivery of Tamoxifen.

Tamoxifen citrate (TMC), a non-steroidal antiestrogen drug used for the treatment of breast cancer, was loaded in a block copolymer of maltoheptaose-b-polystyrene (MH-b-PS) nanoparticles, a potential drug delivery system to optimize oral chemotherapy. The nanoparticles were obtained from self-assembly of MH-b-PS using the standard and reverse nanoprecipitation methods. The MH-b-PS@TMC nanoparticles were characterized by their physicochemical properties, morphology, drug loading and encapsulation efficiency, and release kinetic profile in simulated intestinal fluid (pH 7.4). Finally, their cytotoxicity towards the human breast carcinoma MCF-7 cell line was assessed. The standard nanoprecipitation method proved to be more efficient than reverse nanoprecipitation to produce nanoparticles with small size and narrow particle size distribution. Moreover, tamoxifen-loaded nanoparticles displayed spherical morphology, a positive zeta potential and high drug content (238.6 ± 6.8 µg mL-1) and encapsulation efficiency (80.9 ± 0.4 %). In vitro drug release kinetics showed a burst release at early time points, followed by a sustained release profile controlled by diffusion. MH-b-PS@TMC nanoparticles showed higher cytotoxicity towards MCF-7 cells than free tamoxifen citrate, confirming their effectiveness as a delivery system for administration of lipophilic anticancer drugs.

A critical examination of the DPPH method: Mistakes and inconsistencies in stoichiometry and IC50 determination by UV-Vis spectroscopy.

The DPPH method has been reported with misconceptions in a large number of studies, thus precluding comparison of results. Attention is drawn to a common mistake in the unit used to express the IC50 of ascorbic acid and other antioxidant substances. Concentration of the antioxidant is widely misused with a total disregard for the DPPH• concentration, while the molar ratio of antioxidant/DPPH• would be the correct choice. Data from 26 studies with widely varying IC50 values were renormalized according to reaction stoichiometry, resulting in values which are more coherent and closer to the ideal one of 0.25 for at least 15 of them. In addition, the model which is currently being used to calculate the DPPH• concentration can lead to an overestimation of around 7%, as it does not take into account the small contribution of the reaction product. In view of that, we present a mathematical model to correct the overestimation of the DPPH• concentration.

Curcumin and Quercetin-Loaded Nanoemulsions: Physicochemical Compatibility Study and Validation of a Simultaneous Quantification Method.

Biphasic oil/water nanoemulsions have been proposed as delivery systems for the intranasal administration of curcumin (CUR) and quercetin (QU), due to their high drug entrapment efficiency, the possibility of simultaneous drug administration and protection of the encapsulated compounds from degradation. To better understand the physicochemical and biological performance of the selected formulation simultaneously co-encapsulating CUR and QU, a stability test of the compound mixture was firstly carried out using X-ray powder diffraction and thermal analyses, such as differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA). The determination and quantification of the encapsulated active compounds were then carried out being an essential parameter for the development of innovative nanomedicines. Thus, a new HPLC-UV/Vis method for the simultaneous determination of CUR and QU in the nanoemulsions was developed and validated. The X-ray diffraction analyses demonstrated that no interaction between the mixture of active ingredients, if any, is strong enough to take place in the solid state. Moreover, the thermal analysis demonstrated that the CUR and QU are stable in the nanoemulsion production temperature range. The proposed analytical method for the simultaneous quantification of the two actives was selective and linear for both compounds in the range of 0.5-12.5 µg/mL (R2 > 0.9997), precise (RSD below 3%), robust and accurate (recovery 100 ± 5 %). The method was validated in accordance with ICH Q2 R1 "Validation of Analytical Procedures" and CDER-FDA "Validation of chromatographic methods" guideline. Furthermore, the low limit of detection (LOD 0.005 µg/mL for CUR and 0.14 µg/mL for QU) and the low limit of quantification (LOQ 0.017 µg/mL for CUR and 0.48 µg/mL for QU) of the method were suitable for the application to drug release and permeation studies planned for the development of the nanoemulsions. The method was then applied for the determination of nanoemulsions CUR and QU encapsulation efficiencies (> 99%), as well as for the stability studies of the two compounds in simulated biological fluids over time. The proposed method represents, to our knowledge, the only method for the simultaneous quantification of CUR and QU in nanoemulsions.

Polymer-Decorated Cellulose Nanocrystals as Environmentally Friendly Additives for Olefin-Based Drilling Fluids.

In this study, we intended to evaluate the performance of olefin-based drilling fluids after addition of cellulose nanocrystal (CNC) derivatives. For this purpose, firstly, cellulose nanocrystals, produced from sulfuric acid hydrolysis of cotton fibers, were functionalized with poly(N-isopropylacrylamide) (PNIPAM) chains via free radicals. The samples were then characterized via Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), confocal microscopy, dynamic light scattering (DLS), and zeta potential measurements in water. The FTIR and NMR spectra exhibited the characteristic signals of CNC and PNIPAM groups, indicating successful grafting. As expected, X-ray diffractograms showed that the crystallinity of CNCs reduces after chemical modification. TGA revealed that the surface-functionalized CNCs present higher thermal stability than pure CNCs. The confocal microscopy, zeta potential, and DLS results were consistent with the behavior of cellulose nanocrystals decorated by a shell of PNIPAM chains. The fluids with a small amount of modified CNCs presented a much lower volume of filtrate after high-temperature and high-pressure (HTHP) filtration tests than the corresponding standard fluid, indicating the applicability of the environmentally friendly particles for olefin-based drilling fluids.

Effect of mono- and dicationic ionic liquids on the viscosity and thermogelation of methylcellulose in the semi-diluted regime.

Thermoreversible hydrogels are suitable in food products in order to improve texture and in biomedical applications as drug delivery vehicles. The properties of hydrogels affect their performance in those applications. In this paper, it is presented the effect of mono- (CnMIMBr) and dicationic (Cn(MIM)2Br2) imidazolium ionic liquids (ILs) on the viscosity and gelation of methylcellulose (MC) using rheology, micro differential scanning calorimetric and small angle X-ray scattering (SAXS) techniques. Results show that the ILs affect the pattern of the sol-gel transition and display transition from the salt-out to the salt-in on the gelation temperature, decrease the gel strength and increase viscosity of MC solutions. This behavior can be explained by hydrophobic interaction between the ILs and the MC, which depends of the alkyl chain length of the ILs, type of ILs (conventional or bolaform) and the range of ILs concentration. In general, the presence of ILs decrease the MC gel strength, while dicationic ILs hampers their association on MC in comparison with monocationic ones. The findings highlight the role of ILs on gelation of MC opening possibilities for the design of new complex formulations.

Thermodynamic Insights into the Binding of Mono- and Dicationic Imidazolium Surfactant Ionic Liquids with Methylcellulose in the Diluted Regime.

Alkylimidazolium salts are an important class of ionic liquids (ILs) due to their self-assembly capacity when in solution and due to their potential applications in chemistry and materials science. Therefore, detailed knowledge of the physicochemical properties of this class of ILs and their mixtures with natural polymers is highly desired. This work describes the interactions between a homologous series of mono- (CnMIMBr) and dicationic imidazolium (Cn(MIM)2Br2) ILs with cellulose ethers in aqueous medium. The effects of the alkyl chain length (n = 10, 12, 14, and 16), type, and concentration range of ILs (below and above their cmc) on the binding to methylcellulose (MC) were evaluated. The thermodynamic parameters showed that the interactions are favored by the increase of the IL hydrocarbon chain length, and that the binding of monocationic ILs to MC is driven by entropy. The monocationic ILs bind more effectively on the methoxyl group of MC when compared to dicationic ILs, and this outcome may be rationalized by considering the structural difference between the conventional (CnMIMBr) and the bolaform (Cn(MIM)2Br2) surfactant ILs. The C16MIMBr interacts more strongly with hydroxypropylcellulose when compared to methylcellulose, indicating that the strength of the interaction also depends on the hydrophobicity of the cellulose ethers. Our findings highlight that several parameters should be taken into account when designing new complex formulations.

Evaluation of photodynamic activity, photostability and in vitro drug release of zinc phthalocyanine-loaded nanocapsules.

Nanocapsule formulations containing zinc phthalocyanine (ZnPc) were investigated as drug delivery systems for use in photodynamic therapy (PDT). ZnPc loaded chitosan, PCL, and PCL coated with chitosan nanocapsules were prepared and characterized by means of their physicochemical properties, photodynamic activity, photostability and drug release profile. All formulations presented nanometric hydrodynamic radius, around 100 nm, low polydispersity index (0.08-0.24), slightly negative zeta potential for PCL nanoparticles and positive zeta potential for suspension containing chitosan. Encapsulation efficiencies were higher than 99%. The capacity of ZnPc loaded nanocapsules to produce cytotoxic singlet oxygen ((1)O2) by irradiation with red laser was monitored using 1.3-diphenylisobenzofuran as a probe. The singlet oxygen quantum yields (ΦΔ) for ZnPc loaded chitosan nanocapsules were high and similar to that of the standard (ZnPc in DMSO), displaying excellent ability to generate (1)O2. The photosensitizer loaded nanocapsules are photostable in the timescale usually utilized in PDT and only a small photobleaching event was observed when a light dose of 610J/cm(2) was applied. The in vitro drug release studies of ZnPc from all nanocapsules demonstrated a sustained release profile controlled by diffusion, without burst effect. The nature of the polymer and the core type of the nanocapsules regulated ZnPc release. Thus, the nanocapsules developed in this work are a promising strategy to be employed in PDT.

Antimicrobial photodynamic effect of phenothiazinic photosensitizers in formulations with ethanol on Pseudomonas aeruginosa biofilms.

BACKGROUND DATA: Methylene blue (MB) and toluidine blue (TB) are recognized as safe photosensitizers (Ps) for use in humans. The clinical effectiveness of the antimicrobial photodynamic therapy with MB and TB needs to be optimized, and ethanol can increase their antimicrobial effect. Formulations of MB and TB containing ethanol were evaluated for their ability to produce singlet oxygen and their antibacterial effect on Pseudomonas aeruginosa biofilms. METHODS: Photoactivated formulations were prepared by diluting the Ps (250 µM) in buffered water (pH 5.6, sodium acetate/acetic acid), 10% ethanol (buffer: ethanol, 90:10), or 20% ethanol (buffer: ethanol, 80:20). Biofilms also were exposed to the buffer, 10% ethanol, or 20% ethanol without photoactivation. Untreated biofilm was considered the control group. The production of singlet oxygen in the formulations was measured based on the photo-oxidation of 1,3-diphenylisobenzofuran. The photo-oxidation and CFU (log10) data were evaluated by two-way ANOVA and post-hoc Tukey's tests. RESULTS: In all the formulations, compared to TB, MB showed higher production of singlet oxygen. In the absence of photoactivation, neither the buffer nor the 10% ethanol solution showed any antimicrobial effect, while the 20% ethanol solution significantly reduced bacterial viability (P=0.009). With photoactivation, only the formulations containing MB and both 10% and 20% ethanol solutions significantly reduced the viability of P. aeruginosa biofilms when compared with the control. CONCLUSIONS: MB formulations containing ethanol enhanced the antimicrobial effect of the photodynamic therapy against P. aeruginosa biofilms in vitro.

Protective action of ethanolic extract of Rosmarinus officinalis L. in gastric ulcer prevention induced by ethanol in rats.

The pathology of a gastric ulcer is complex and multifactorial. Gastric ulcers affect many people around the world and its development is a result of the imbalance between aggressive and protective factors in the gastric mucosa. In this study, we evaluated the ethanolic extract of Rosmarinus officinalis L. (eeRo); this plant, more commonly known as rosemary, has attracted the interest of the scientific community due to its numerous pharmacological properties and their potential therapeutic applications. Here, we tested the preventive effects of eeRo against gastric ulcer induced by 70% ethanol in male Wistar rats. In addition, we aimed to clarify the mechanism involved in the preventive action of the eeRo in gastric ulcers. Based on the analysis of markers of oxidative damage and enzymatic antioxidant defense systems, the measurement of nitrite and nitrate levels and the assessment of the inflammatory response, the eeRo exhibited significant antioxidant, vasodilator and antiinflammatory properties.

Effect of bleaching agents on the fluorescence of composite resins.

As the demand for an esthetically satisfactory smile has increased, interest in less invasive procedures, such as composite restoration and tooth bleaching, has also increased. Composite resins exhibit several optical properties, including fluorescence, which are intended to mimic the natural dentition. The aim of this study was to evaluate the effect of hydrogen peroxide (HP) bleaching protocols for home and in-office applications on the fluorescence of composite resins. Sixty composite resin specimens (shade A2) were divided into 2 groups of 30 each according to the material type (groups R1 and R2 were made up of 4 Seasons and Opallis specimens, respectively). Each group was subdivided into 3 subgroups (n = 10) according to the bleaching protocol administered: home application (HP 7.5%); in-office application (HP 35%); and control (Co), immersion in deionised water. The fluorescence intensities were measured before and after the bleaching treatments using a Cary Eclipse fluorescence spectrophotometer and statistically analysed by paired t test, Student's t test, analysis of variance (ANOVA), and Tukey's multiple comparison test (P < 0.05). Significant differences between groups R1 and R2 after the different treatments were noted. The fluorescence intensities differed across the subgroups after 30 days of treatment. The HP 7.5% protocol induced the greatest change in the fluorescence intensities among the specimens in the R1 group.

Degradation of Direct Black 38 dye under visible light and sunlight irradiation by N-doped anatase TIO2 as photocatalyst.

The N-doped TiO(2) photocatalyst was prepared by calcination of a hydrolysis product composed of titanium (IV) isopropoxide with ammonia as the precipitator. X-ray diffraction, surface area, XPS and UV-vis spectra analyses showed a nanosized anatase structure and the appearance of a new absorption band in the visible region caused by nitrogen doping. The degradation of Direct Black 38 dye on the nitrogen-doped TiO(2) photocatalyst was investigated under visible light and sunlight irradiation. The N-doped anatase TiO(2) demonstrated excellent photocatalytic activity under visible light. Under sunlight irradiation, the N-doped sample showed slightly higher activity than that of the non-doped sample.